In a spray-drying process there are two opposing factors; the more water which is present in the crutcher slurry, the more has to be evaporated, with a resultant increase in costs. Against that, the less water present, the more viscous the crutcher slurry becomes, until a point is reached where it cannot be pumped and metered. An additional factor, however, is that the market is beginning to move towards denser products. Whereas ten years ago a spray-dried detergent powder could have an ex-factory bulk density of 500 g/liter, nowadays a bulk density of 600 to 650 g/liter or more might be required. It is now generally accepted that, other things being equal, spray-drying of a slurry having a low water content leads to a high bulk density product, and so industrial research began to seek ways of spray-drying low water content crutcher slurries without encountering the problem of high slurry viscosity.
We have now discovered a crutcher slurry composition which exhibits exceptionally low viscosity even at low water content, enabling it to be spray-dried to a high bulk density detergent powder.